Nuclear kinetic energy spectra of D_2^+ in intense laser field: Beyond Born Oppenheimer approximation

Simultaneously, the vibrational nuclear dynamics and full dimensional electronic dynamics of the deuterium molecular ion exposed to the linear polarized intense laser field are studied. The time dependent Schr\"odinger equation of the aligned D2+ with the electric laser field is solved for the simulation of the complicated dissociative ionization processes and compared with the recent related experimental results. In this work, the R-dependent ionization rate and the enhanced ionization phenomenon beyond the Born-Oppenheimer approximation (BOA) are introduced and calculated. The substructure of the nuclear kinetic energy release spectra are revealed as the Coulomb explosion energy spectra and dissociation energy spectra in the dissociation-ionization channel. The significant and trace of these distinct sub-spectra in the total spectra comparatively are displayed and discussed.Comment: 17 pages, 4 figure

Detailed instantaneous ionization rate of H2+_2^+ in intense laser field

Component instantaneous ionization rate (IIR) is introduced and the approach of its calculation is formulated. The component IIR's and the overall (time-averaged) component ionization rates are calculated for H$_2^+$ at different values of inter-nuclear distance in a linearly polarized laser field with $1.0 \times10^{14}$W cm$^{-2}$ intensity and $\lambda \sim 1064$nm wavelength by direct numerical solution of the fixed-nuclei full dimensional time-dependent Schr \"odinger equation. The exact overall component ionization rates calculated by time-averaging of the component IIR are compared with those calculated approximately via the virtual detector method (VD). Details of the time dependent behavior of the outgoing and incoming electron wavepackets of the H$_2^+$ system in intense laser field at sub-femtosecond time scale are studied based on the calculated component IIR. It is shown clearly that the positive (outgoing electron wavepacket) signals of the IIR and its z component are strong and sharp but the negative (returning electron wavepacket) signals of the IIR are smooth and weak. The structure of the $\rho$ component of the IIR has smooth structure. Relation between the R-dependent ionization rate and duration of the ramp of the laser pulse is studied and it is explicitly shown that for internuclear distance R<5.6, when the laser pulse is turned on without a ramp, the first peak of R-dependent ionization rates moves towards the peak of the lower time dependent Floquet quasi-energy state (QES).Comment: 28 pages, 7 figure

Nuclear classical dynamics of H2_2 in intense laser field

In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization respectively. In the second part of the paper, the time dependent Schr\"{o}dinger and Newton equations are solved simultaneously for the electrons and the nuclei of H$_2$ respectively. The electrons and nuclei dynamics are separated on the base of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390 nm, 532 nm and 780 nm) and intensities ($5\times10^{14}$ $Wcm^{-2}$ and $5\times10^{15}$ $Wcm^{-2}$) of the ultrashort intense laser pulses with a sinus second order envelope function are used. The behaviour of the time dependent classical nuclear dynamics in the absence and present of the laser field are investigated and compared. In the absence of the laser field, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.Comment: 16 pages, 7 figure